The invention relates to a method and an apparatus for providing a temporary enrichment of the fuel-air mixture fed to an internal combustion engine during acceleration. The method and apparatus of the invention may be used with a fuel mixture preparation system of any kind and is based on monitoring the pressure changes in the induction manifold of the engine during acceleration. The invention relates particularly well to continuous electronic injection systems in which the fuel-air ratio is controlled by a control pressure of hydraulic fluid and wherein the control pressure is altered by the method and apparatus of the invention so as to superimpose on the control process already present an additional change for the purpose of fuel mixture enrichment. The continuous fuel injection system to which this invention may be particularly adapted may especially be operating under the control of an oxygen sensor which monitors exhaust gas composition, i.e. a so-called .lambda. control process.
Known fuel mixture preparation systems for internal combustion engines of motor vehicles normally include a provision for admitting additional fuel for engine acceleration. In the simplest case, a carburetor may be equipped with a so-called accelerator pump which supplies additional raw fuel when the gas pedal is depressed. In known electronic fuel injection systems, an enrichment during acceleration may take place on the basis of the motions of a baffle plate in the induction manifold which responds to the changing air flow rate and which may be part of a so-called air flow rate meter.